Determination of CaO Carbonation Kinetics under Recarbonation Conditions

Abstract

This work investigates the kinetics of the reaction of CO 2 with CaO particles partially carbonated that are forced to increase their carbonate content at high temperatures in an atmosphere of rich CO 2 . This additional recarbonation reaction on particles that have already completed their fast carbonation stage is the basis of a novel process that aims to increase the CO 2 carrying capacity of sorbents in calcium looping CO 2 capture systems. The CaO reaction rates and the maximum carbonation conversions after the recarbonation step were measured on a thermogravimetric analyzer, and the results indicate that they are highly dependent upon the temperature and CO 2 partial pressure, with steam also being a contributing factor. The reaction mechanism governing the reaction rates during the carbonation and recarbonation reactions is explained by the combined control of the chemical reaction and CO 2 diffusion through the CaCO 3 product layer. An extension of the random pore model adapted to multi-cycled CaO particles was successfully applied to calculate the CaO molar conversion as a function of the time and the recarbonation conditions, using kinetic parameters consistent with previously published results on carbonation kinetics under typical flue gas conditions.